For all people using speech language, it is very important to detect the symptoms of a laryngeal disease like an abnormal voice as soon as possible for the quick recovery and to find medical treatments. This study is to clarify a phonatory mechanism, and aims to be applied to the medical treatment support technology. For that purpose, in vitro experiment using elastic thin film modeled after human vocal folds was performed. In the experiment, the glottal width and amplitude were measured using high speed video camera and microphone with the glottal width and the anterior commissure angle were changed gradually. As a result, it was found that the laryngeal source was generated when glottis was open and closed, and the vibration sound was generated when the anterior commissure angle was over 6 deg.